1. Field of the Invention
The present invention relates to disk drives; more particularly, to hard (or fixed) disk drives.
2. Description of the Related Art
Developments in personal computers, portable computers and lap top computers have prompted reductions in the size and increases in memory capacity of disk drives. Attempts to provide further reductions in the size and weight, and increases in durability and memory capacity of existing disk drives have been met with limited success. The size (particularly the height) and weight of fixed or hard disk drives and the inability of existing hard disk drives to withstand physical shocks and/or vibrations have been factors which have prevented the incorporation of fixed disks in lap-top and in some cases even larger portable computers.
Existing disk drives incorporate a large number of mechanical parts. Each part in a disk drive also represents an increase in the weight of the drive and the space occupied by the drive. A large number of mechanical components makes manufacturing difficult and expensive and increases the possibility and probability of the mechanical failure of the drive. Importantly, the number of mechanical components is related to the ability of the drive to survive physical shocks and vibrations.
Resistance to physical shocks and vibrations is critical to protecting the disk or disks, the head or heads, and the various bearings in a disk drive from damage; in particular, it is necessary to prevent damage to the disks which can cause a loss of data, and damage to the heads or the bearings which can end the life of a drive, resulting in a total loss of data. Prior disk drives, however, have limited resistance to physical shocks. Resistance to physical shocks is of paramount importance in portable computers.
In conventional drives mechanical distortion or flexing of the mechanical components of a disk drive which support the heads and disks causes tracking problems by moving the heads, which are mounted at one point on the supporting components, relative to the disk, which is mounted at another point on the supporting components. The heads associated with the top and bottom surfaces of a disk can move relative to the disk to the point where the different heads are in different cylindersxe2x80x94a cylinder being defined as a vertical segment representing the same track on the top and bottom surfaces of a disk. This problem is known as mechanical off-track and is compounded by increased track densities.
Another problem with prior disk drives is the difficulty in sealing the drive to protect the disks from contaminants. This difficulty arises in part, from the large number of points at which access is provided to the environment in which the disk resides. These access points are utilized to bring to the interior of the disk drive electrical circuits which provide current to the motor which rotates the disk, transmit data signals to and from heads which read and record information on the disks, and in some instances, provide current to a voice coil for positioning the head (or heads) with respect to the disk or disks.
Many of these disadvantages of prior disk drives are attributable to the casingxe2x80x94a three-dimensional casting or so-called xe2x80x9ctoilet bowlxe2x80x9dxe2x80x94in which the disks reside. Such a casing is a large, three dimensional piece of cast metal, usually aluminum, having a round portion where the disks residexe2x80x94hence the name xe2x80x9ctoilet boil.xe2x80x9d A top plate covers the entire open top of the casing, forming a seal therewith.
The spindle on which the disks rotate is supported by and extends through both the casing and the cover.
The protrusion of the spindle through the casing and the cover provides possible points of entry for contaminants. Further, in disk drives using stepper motors to position the heads with respect to the disk, the stepper motor is located outside of the casing, requiring a seal between the stepper motor and the casing. Acknowledging the existence of points where contaminants can enter the disk drive, manufacturers of conventional disk drives provide a breather filter and design the disk drives so that the rotation of the disks causes the disk drives to exhaust air through leaks in the seals and to intake air only through the breather filter. However, a fairly course filter must be provided in the breather filter for a flow of air to exist, and thus contaminants enter the disk drive through the filter paper.
A cast casing is difficult to manufacture with precision, particularly the location of mounting points for elements of the drive supported by the casing. Mounting holes must be drilled after the casing is cast, and the mounting holes must be aligned with the casing and with each other. More importantly, however, a three-dimensional, cast casing flexes due to thermal stresses causing the above-mentioned mechanical off-track problems.
In conventional disk drives which use a voice coil to pivot an actuator arm in order to position the heads with respect to the disk, a flex circuit, having one end attached to the actuator arm and the other end attached to a fixed point in the disk drive, transfers the information signals to and from the heads. The standard orientation of such a flex circuit is a loop extending away from the disk. The distance between the point at which the flex circuit is attached to the actuator and the end of the disk drive is limited, and thus the radius of the arc or curve of the flex circuit is small and the length of the flex circuit itself is limited. Therefore, the entire flex circuit moves when the actuator arm is pivoted and a torque is exerted on the actuator arm by the flex circuit. The torque exerted on the actuator arm must be compensated for, either added to or subtracted from the torque created by the voice coil, when performing a seek operation. This compensation is complicated by the fact that the torque exerted on the actuator by the flex circuit varies with the position of the actuator.
Various types of locking (or latch) devices have been used to lock the arm of a voice coil in a particular position when the disk drive is not operating. The trend in latch devices is to utilize a high power unit which is separately assembled to provide reliability. However, high power latch devices generate a large amount of heat which is not desirable in a disk drive or any other area in a computer. Further, the operation of conventional latch devices can be position dependent. Thus, the orientation of the disk drive and the computer in which the disk drive is installed could effect the reliability of the latch device. Such a positional dependence of reliability is not satisfactory for portable computers.
With the ever increasing storage capacity available on individual magnetic disks, and the ever increasing speed at which microprocessors such as Intel""s 80386 and 80486 chips operate, the data access time of the disk drive is critical to overall system performance. In many cases, the speed at which the disk accesses data and provides it to the microprocessor is the main performance bottleneck in the system. One critical factor in disk access time is the xe2x80x9cseek timexe2x80x9d of a drive, generally defined as the time the actuator takes to access particular data at a particular track location on the magnetic disk. The total access time is generally a function of the efficiency of the actuator motor in moving the read/write heads along the arcuate path between consecutive tracks of the disk, and the data throughput of the control electronics.
It is, therefore, an object of the present invention to provide a disk drive having a low height and a low weight.
A further object of the present invention is to provide a multiple platter (disk), disk drive having a one inch height form factor.
Another object of the present invention is to provide a disk drive which is resistant to damage from physical shocks.
Another object of the present invention is to provide a low height disk drive having an increased data storage capacity.
Another object of the present invention is to provide a disk drive in which any mechanical off tracking of the heads is mechanically minimized and electronically corrected.
Another object of the present invention is to provide a disk drive assembly in which a single electrical connector transfers all electrical currents and data signals from the environment in which the disks reside to the exterior of the environment, and in which a header which communicates those electrical signals through the base plate is the only communication between the interior and exterior of the drive.
Another object of the invention is to provide an improved voice coil motor design, and specifically a disk drive having an efficient actuator positioning mechanism.
These and other objects of the present invention are provided by a disk drive, including: a head-disk assembly, having a base having a top and a bottom, storage means, supported on said top of said base, for storing data, solid storage means comprising two disks, interactive means for reading information from and writing information on said disks, actuator means, supported on said base and responsive to control signals, for selectively positioning said interactive means with respect to said disks means, and a cover sealably attached to said base to enclose said disks, said interactive means, and said actuator means; and control means, mounted on said head-disk assembly so that said control means is adjacent to said bottom of said base, for generating control signals to control said actuator means and for providing information signals to and receiving information signals from said interactive means, said head-disk assembly, said control means having an overall maximum height of approximately one inch (1xe2x80x3).
A specific advantage of the present invention is that the disk drive has a reduced height with respect to conventional disk drives utilizing disks of approximately the same diameter. In particular, the three and one-half inch (3.5xe2x80x3) single platter and multiple platter drives of the present invention have an overall height of one inch (1xe2x80x3). Furthermore, the disk drive of the present invention is light in weightxe2x80x94the drives of the present invention weighs slightly more than one pound.
A further advantage of the present invention is that a single electrical connector (header) transfers all electrical signals between the exterior and the interior of the casing, thereby reducing the possibility of the introduction of contaminants into the controlled environment within the casing. Importantly, the disk drive of the present invention does not require a breather filter.
A further advantage of the disk drive of the present invention is that it includes a voice coil actuator assembly including means for mounting a plurality of read/write heads with respect to a storage means; and means for positioning said mounting means at a plurality of positions with respect to said disk, wherein said means for positioning has relatively equal efficiency between the inside diameter and the outside diameter of the disk.